In an electro-photographic type image forming apparatus where the distance from position for writing the image onto the photoreceptor to the position for transfer of the image to a sheet is long (this distance is long especially in the color tandem type image forming apparatus using intermediate transfer member), sometimes the image is already being formed on the photoreceptor or the intermediate transfer member at the point when it is detected that there are no more sheets in the sheet feeding tray.
In this case, because the image that was formed cannot be transferred to the sheet, the untransferred toner on the photoreceptor or the intermediate transfer member needs to be cleaned using a cleaning blade or the like. This causes cleaning off a great deal of untransferred toner, thus resulting in faster deterioration of the photoreceptor, intermediate transfer member and cleaning blade. In addition, this causes excess toner to be consumed.
In order to solve the foregoing problems, the Patent Document 1 describes that the sheet feeding interval and the image interval are lengthened and the writing starting point is delayed behind the sheet feeding starting point so as to avoid unnecessary image formation in the case where the number of remaining sheets in the feeding tray becomes small.
Patent Document 1: Unexamined Japanese Patent Application Publication No. 2001-337575.
However, in the method described in the Patent Document 1, the sheet feeding interval is lengthened when the number of sheets remaining in the sheet feeding tray becomes low and thus productivity is reduced.
The present invention was conceived in view of the foregoing problems and an object thereof is to provide an image forming apparatus that controls unnecessary image formation without reducing productivity.